Automotive cooling fan with biased flexible blades

Abstract

A flexible bladed automotive cooling fan comprising biasing members biasing both the upstream and downstream sides of th blades including a root portion of the upstream biasing member extending beyond the remainder of both biasing members, the blade thereby having a substantially increased natural frequency and a reduced amplitude of vibration at resonance as well as an improved airfoil configuration.

What is claimed is: 
     
       1. An automotive cooling fan comprising a hub and a plurality of fan blade assemblies, each assembly comprising: an arm extending radially outwardly from said hub, and a flexible, resilient blade connected to said arm, said blade extending radially from a root portion adjacent said hub to a tip portion remote from said hub and extending transversely from a leading portion adjacent said arm to a trailing edge, relative to the direction of fan rotation, said arm, and said blade curved between said leading portion and said trailing edge presenting a convex surface on the upstream side, defined by the direction of airflow, and a concave surface on the downstream side of said blade, said blade adapted to decamber in an upstream direction with increasing rotational speed, characterized in that said assembly also comprises: a flexible, resilient biasing member connected to said arm on the upstream side of said blade; said biasing member curved in a downstream direction on a smaller radius than that of said blade, contacting said blade behind said arm and biasing said blade in a downstream direction when said fan is stationary; said biasing member comprising a root portion overlying said blade root portion of an outer portion extending radially outwardly from said biasing member root portion; said biasing member outer portion contacting said blade along a line generally radially extending outwardly from said root portion at a first limited distance behind said arm and said biasing member root portion contacting said blade root portion at a second limited distance behind said arm greater than said first distance.   
     
     
       2. The fan claimed in claim 1 further characterized in that said second distance is at least 50% of the width of said blade behind said arm. 
     
     
       3. The fam claimed in claim 1 further characterized in that said fan blade assembly also comprises a flexible, resilient downstream biasing member connected to said arm and extending radially along the downstream side of the blade leading portion from the root to the tip portions of said blade, said downstream biasing member extending transversely from said leading portion a limited distance toward said trailing edge engaging said blade behind said arm and between said leading portion and said trailing edge and biasing said blade in an upstream direction. 
     
     
       4. The fan claimed in claim 3 further characterized in that said downstream biasing member extends transversely, contacts and biases said blade at a third limited distance between said first and second distances. 
     
     
       5. The fan claimed in claim 4 further characterized in that said second distance is at least 50% of the width of said blade behind said arm. 
     
     
       6. An automotive cooling fan comprising a plurality of radially extending flexible resilient blades connected to radially extending arms, said blades extending transversely from leading portions adjacent said arms to trailing edges behind said arms and curved therebetween to present a convex surface on the upstream side and a concave surface on the downstream side of said blades, characterized in that flexible resilient first biasing means are provided on the upstream sides of said blades engaging and biasing said blades in a downstream direction, said biasing means engaging the radially inner root portions of said blades behind said arms at a position at least 50% of the blade width behind said arms and engaging the radially outer portions of said blades along a line extending radially behind said arms at a distance therebehind less than the distance behind said arms at which root portions of said blades are engaged and said biasing means engaging said root portions of said blades with a greater biasing force than said outer portions of said blades. 
     
     
       7. The fan claimed in claim 6 further characterized in that second biasing means are provided on the downstream sides of said blades engaging and biasing said blades in an upstream direction, said second biasing means engaging said blades radially therealong behind said arms between the points of engagement with said blades of said first biasing means.